The present invention relates to a multilayer printed-circuit board in which wiring can advantageously be done with an ultra-high density, a multilayer-printed-wiring board obtained by forming a build-up printed-wiring layer on the multilayer printed-circuit board, and a semiconductor device including semiconductor components mounted on the multilayer printed-circuit board or multilayer printed-wiring board.
The present invention relates more particularly to a multilayer printed-circuit board formed by stacking a plurality of singe-sided circuit boards one on the other, each having a plurality of filled via-hole formed therein, with an adhesive applied between them, and heating and pressing them together or by laminating a single-sided circuit board on either side of a double-sided circuit board as a core with an adhesive applied between the single-side circuit boards and double-sided circuit board, and heating and pressing the circuit boards together, a multilayer printed-wiring board obtained by forming a build-up wiring layer on at least one side of the multilayer printed-circuit board, and a semiconductor device using the multilayer printed-circuit board or multilayer printed-wiring board.
Along with the recent innovation of the electronic technology, the electronic devices have been designed to have a reduced physical size and operate at a higher speed, and thus the package circuit board on which IC chips are mounted has been required to have a correspondingly higher packaging density due to a finer pattern and operate with a correspondingly higher reliability.
Such a package circuit board is known from the disclosure in the monthly journal xe2x80x9cSurface Mount Technologyxe2x80x9d, January issue, 1997. This conventional package circuit board has a build-up multilayer wiring layer formed on either side of a multilayer core circuit board.
In the above conventional package circuit board, however, a conductor layer in a multilayer core circuit board and build-up multilayer wiring layer are connected to each other by providing on the surface of the core multilayer circuit board an inner pad wired from through-holes and connecting via-holes to the inner pad. Thus, the land of each through-hole takes the form of a dumbbell or the like, the inner pad hinders through-holes from being disposed with an improved higher density, and only a limited number of through-holes can be formed. Hence, if the core circuit board is formed multilayered to increase the wiring density, it is not possible to assure a sufficient electrical connection between outer build-up wiring layers and conductor layers in the multilayer core circuit board.
The Inventors of the present invention proposed a method for overcoming the above-mentioned drawbacks of the prior art in the Japanese Patent Application No. 10-15346 (Unexarnined Patent Publication No. 214846/""99).
The multilayer printed-wiring board disclosed by the Inventors of the present invention in the above Unexamined Patent Publication No. 214846/""99 includes a build-up wiring layer formed by stacking interlinear insulative resin layers and conductor layers alternately one on the other on a multilayer core circuit board having an inner conductor layer and connecting the conductor layers to each other by via-holes, the core multilayer circuit board having formed therein through-holes each filled with a filler, a conductor layer being formed to cover an exposed surface of the filler from the through-holes, the via-holes being connected to the conductor layer, whereby the through-holes are disposed with an improved density and the conductor layer can positively be connected to the conductor circuit in the core multilayer circuit board via the through-holes disposed with the high density.
However, the through-hole in the multilayer printed-wiring board is formed by forming holes through a core multilayer circuit board using a drill or the like and by electroless-plating the wall surface and board surface of the drilled hole. Thus, when the precision and cost of forming the through-hole are taken in consideration, the lower limit of the opening diameter of such a through-hole is on the order of 300 xcexcm. To realize the ultrahigh density of wiring demanded from the present electronic industries, there should desirably developed techniques capable of attaining a smaller opening diameter of the through-hole ranging from 50 to 250 xcexcm and a smaller through-hole land pitch.
To meet the above demand, the Inventors of the present invention formed a core multilayer circuit board by preparing a plurality of circuit boards having a conductor circuit formed on one or either side of a core substrate made of a hard material and a plurality of filled via-hole formed through the core substrate to extend from the one side thereof to the conductor circuit, by stacking the plurality of circuit boards one on the other with an adhesive applied between them, and then heating and pressing of the circuit boards together. With this core multilayer circuit board, it was found that even with the no through-hole provided in the core multilayer circuit board, sufficient electrical connections can be made between the conductor circuits in the core multilayer circuit board, and conductor circuits in the core multilayer circuit board and build-up wiring layers formed on the core multilayer circuit board, by a plurality of filled via-hole formed in the core multilayer circuit board and those formed in the build-up wiring layer right above the core multilayer circuit board.
The multilayer printed-circuit board has various electronic components including a semiconductor chip such as LSI and the other mounted on the outermost surface thereof. The methods of mounting the electronic components include a pin mounting technology in which part holes into which terminals of the electronic component are to be introduced are formed in place on the conductor circuit formed on the outermost surface while connection lands whose diameter is slightly larger than that of the part hole are formed around the part holes, and a group of leads of the electronic component is connected, by soldering, to the part holes and connection lands, and a surface mounting technology in which a cream solder is applied to a land formed in place on the conductor circuit in advance, terminals of an electronic component are placed in contact with the cream solder and then the cream solder is made to reflow in an atmosphere maintained at the melting temperature of the solder to connect the electronic component.
When any of such mounting methods is employed to connect an electronic component, however, it is indispensable to form on the conductor circuit a land having an appropriate diameter. Nevertheless, in case an increased number of electronic components is to be mounted on the multilayer printed-circuit board because of the reduced physical sizes and higher functions of the recent electronic devices, the total area of such lands has to be too large to neglect, which stands in the way of attaining a higher packaging density.
Also, when soldering for connection of an electronic component, it is indispensable to previously apply a solder resist to the electronic component in order to prevent a melted solder from flowing to an unintended position where such flow is not desirable and causing a short-circuit, break or the like. Thus, the multilayer printed-circuit board has to be designed for an extra gap between wires with consideration given to a possible misregistration in the solder resist printing, which also stands in the way of attaining the higher packing density.
Accordingly, the present invention has an object to overcome the above-mentioned drawbacks of the prior art by providing a multilayer printed-circuit board and multilayer printed-wiring board in which wiring can be done with a high density and on which electronic components can be mounted with a high density, and a semiconductor device using the multilayer printed-circuit board and wiring board.
The Inventors of the present invention have made various studies to attain the above object, and worked out the following inventions which will be outlined herebelow:
(1) The above object can be attained by providing a multilayer printed-circuit board formed by stacking one on the other a plurality of circuit boards, each including a hard insulative substrate having a conductor circuit formed on one or either side thereof, and having formed therein at least one via-hole being a hole formed through the hard insulative substrate to extend to the conductor circuit and each filled with a conductive substance, with an adhesive applied between the plurality of circuit boards, and heating and pressing the circuit boards together,
one of the outermost ones of the stacked circuit boards having formed on the surface thereof at least one conductive bump positioned right above the via-hole and electrically connected to the via-hole; and
the other outermost one of the stacked circuit boards having formed on the surface thereof at least one conductive pin or ball positioned right above the via-hole and electrically connected to the via-hole.
(2) Also the above object can be attained by providing a multilayer printed-circuit board formed by stacking one on the other:
a plurality of single-sided circuit boards, each including a hard insulative substrate having a conductor circuit formed on one side thereof, and having formed therein at least one via-hole being a hole formed through the hard insulative substrate to extend to the conductor circuit and each filled with a conductive substance; and
a single-sided circuit board including a hard insulative substrate having at least one conductor circuit formed on one side thereof and at least one hole formed through the hard insulative substrate to extend to the conductor circuit, with an adhesive applied between the single-sided circuit boards, and heating and pressing the single-sided circuit boards together,
one of the outermost ones of the stacked circuit boards having formed on the surface thereof at least one conductive bump positioned right above the via-hole and electrically connected to the via-hole; and
the other outermost one of the stacked circuit boards having formed on the surface thereof at least one conductive pin or ball positioned right above the via-hole and electrically connected to the via-hole.
Preferably in the multilayer printed-circuit board described in the above paragraph (1), one of the outermost ones of the plurality of circuit boards should have formed on the surface thereof a solder resist layer covering the conductor circuit, and right above the via-hole a conductive bump connecting to a conductive layer or via-hole exposed from a hole formed in the solder resist layer, and the other outermost circuit board should have formed on the surface thereof a solder resist layer covering the conductor circuit, and right above the via-hole a conductive pin or ball connecting to a conductive layer or via-hole exposed from a hole formed in the solder resist layer.
In the multilayer printed-circuit boards described in the above paragraph (1) or (2), the distance between the neighboring via-holes formed in each of the circuit boards should desirably be increased as it goes from one of the circuit boards towards the other.
(3) Also the object can be attained by providing a semiconductor device including the above multilayer printed-circuit board described in the above paragraph (1) or (2) and at least one electronic component electrically connected to the conductive bumps formed on one of the outermost circuit boards of the multilayer printed-circuit board.
In the semiconductor device described in the above paragraph (3), it is desirable that the circuit board on which at least one electronic component is mounted should have a stiffer provided along the circumference thereof and a chip capacitor should be electrically connected to the one of the via-holes formed in the outermost circuit board opposite to that outermost circuit board on which the electronic component is mounted and which is located in a position opposite to the position where the electronic component is mounted.
(4) Also the above object can be attained by providing a semiconductor device including a multilayer printed-circuit board formed by stacking one on the other a plurality of circuit boards, each including a hard insulative substrate having at least one conductor circuit formed on one or either side thereof, having formed therein at least one via-hole being a hole formed through the hard insulative substrate to extend to the conductor circuit and each filled with an electro-plating substance, and including at least one projecting conductor, each electrically connected to the via-hole, with an adhesive applied between the plurality of circuit boards, and heating and pressing the circuit boards together, and at least one electronic component such as LSI chip, electrically connected to the outermost circuit board of the multilayer printed-circuit board,
one of the outermost ones of the stacked circuit boards having formed on the surface thereof at least one conductive bump positioned right above the via-hole and each electrically connected to the via-hole, and the electronic component being electrically connected to the conductive bumps;
the other outermost circuit board opposite to the outermost circuit board on which the electronic component is mounted having provided on the surface thereof at least one chip capacitor, each electrically connected to the via-hole positioned beneath the electronic component.
In the semiconductor device described in the above paragraph (4), the circuit board on which the electronic component is mounted should desirably have a board warp-preventive stiffener secured by bonding to the circumference thereof.
(5) Also the above object can be attained by providing a multilayer printed-circuit board including a core multilayer circuit board having an inner conductor circuit, having formed on one or either side thereof a build-up wiring layer formed from interlaminar insulative resin layers and conductor layers alternately stacked one on the other, the conductor layers being connected to each other by at least one via-hole,
the core multilayer circuit board being formed by stacking one on the other a plurality of circuit boards, each including a hard insulative substrate having at least one conductor circuit formed on one or either side thereof, and having formed therein at least one via-hole being a hole formed through the hard insulative substrate to extend to the conductor circuit and each filled with a conductive substance, with an adhesive applied between the plurality of circuit boards, and heating and pressing the circuit boards together.
In the multilayer printed-circuit board described in the above paragraph (5), it is desirable that the build-up wiring layer should be formed on either side of the core multilayer circuit board, the outermost conductor layer forming one of the build-up wiring layers have at least one solder bump formed on the surface thereof and the other outermost conductor layer forming the other build-up wiring layer have at least one conductive pin or ball formed on the surface thereof.
Also, according to the present invention, there is provided a multilayer printed-wiring board suitable for use as a mother board, in which the outermost conductor layers forming the build-up wiring layer are covered each with a solder resist layer and the outermost conductor layer exposed from the hole formed in the solder resist layer is formed as a conductor pad (or in the form of a connection terminal).
Also in the multilayer printed-circuit board described in the above paragraph (5), it is desirable that the build-up wiring layer should be formed on one side of the core multilayer circuit board, at least one solder bump to be connected to an electronic component including a semiconductor chip such as LSI be provided right above the via-hole on the surface of the outermost conductor layer of the build-up wiring layer, and at least one conductive pin or ball to be connected to a mother board be provided right above the filled via-hole on the conductor circuit exposed on the other side of the core multilayer circuit board. Also, it is desirable that the outermost conductor layer forming the build-up wiring layer and the other side of the core multilayer circuit board should be covered with a solder resist layer, at least one conductor pad be formed on one of the outermost conductive layers, each exposed from a hole formed in the solder resist layer, and at least one conductive pint or ball to be connected to a mother board be formed right above the filled via-hole on the conductor circuit exposed on the other side of the core multilayer circuit board.
In the multilayer printed-circuit boards described in the above paragraphs (1) to (5), the conductive substance should desirably be a metal-plating produced by electro-plating or a conductive paste comprising metal particles and thermosetting or thermoplastic resin.
In the multilayer printed-circuit boards described in the above paragraphs (1) to (5), it is desirable that each circuit board forming the core multilayer circuit board should have at least one projecting conductor provided in a position corresponding to the via-hole and electrically connected to the via-hole and also the projecting conductor be formed from a conductive paste.
Further in the multilayer printed-circuit boards described in the above paragraphs (1) to (5), it is desirable that a part of the via-holes in the build-up wiring layer should be positioned right above those formed in the core multilayer circuit board and connected directly to the via-hole.
Furthermore, in the multilayer printed-circuit boards described in the above paragraphs (1) to (5), it is desirable that the single-/double-sided circuit board as a basic unit forming the core multilayer circuit board should be formed from a selected one of hard substrate materials such as glass epoxy resin, glass bismaleimide-triazine resin, glass polyphenylene ether resin, aramid non-woven fabric-epoxy resin and aramid non-woven fabric-polyimide resin. Also, the circuit board should desirably be formed from a glass epoxy resin of 20 to 100 xcexcm in thickness and the filled via-hole should desirably have a diameter of 50 to 250 xcexcm.
Moreover, the via-hole in each circuit board should desirably be formed from a hole formed by illuminating the surface of the glass epoxy resin substrate with 1 to 50 shots of a carbon-dioxide gas laser whose pulse energy is 0.5 to 100 mJ, pulse width is 1 to 100 xcexcs, pulse interval is 0.5 ms or more.